FIELD OF THE INVENTION
[0001] This invention relates to self-steering axle suspension systems for wheeled vehicles.
More particularly, this invention relates to lockout mechanisms for preventing or
controlling the steerability of such suspension systems.
BACKGROUND OF THE INVENTION
[0002] In recent years, self-steering axle suspension systems, particularly in the medium
and heavy duty truck and semi-trailer industry, have become quite popular. Generally
speaking, such suspensions are made self-steering by adjusting the pitch or caster
angle of the wheels so that the drag of the wheels as the vehicle proceeds in the
forward direction causes the suspension (i.e. the wheels of the system) to steer automatically
in response to steering of the vehicle. Typical of such suspensions are those referred
to as "pusher", "tag" or "trailing" axles found on trucks and semi-trailers. They
may be of the liftable or non-liftable type.
[0003] In most self-steering suspensions in common use, a steering damper or pair of dampers
is used to suppress (dampen) oscillations during road operation of the vehicle. While
such dampers come in a wide variety of styles, one known type is similar in construction
to a conventional shock absorber either with, or without, an external auxiliary coil
spring. Such devices are often referred to as "stabilisers". In such a damper, a large
cylinder is provided which houses a fluid reservoir that is almost completely filled
with a hydraulic (i.e. incompressible) fluid. This cylinder is separated into two
compartments by a piston having an orifice, or orifices, in its head, thus to form
a flow path between the two compartments, but which otherwise seals the two compartments
against fluid flow therebetween. Dampening is accomplished by attaching one end of
the cylinder (usually by a piston rod connected to the piston head) to the steering
mechanism of the suspension and the other end to the axle or beam structure of the
suspension or vehicle (or vice versa). Since the orifice(s) in the piston head restricts
flow between the two compartments as the piston slides in the cylinder due to oscillations
experienced during vehicle operation (e.g. road shocks and wheel "shimmy"), such oscillations
are appropriately dampened and tracking is stabilized.
[0004] In self-steering suspensions the castor angle, as aforesaid, is appropriately adjusted,
in a conventional manner, to create steering during vehicle forward motion (e.g. as
the vehicle goes into a turn). When the vehicle is backed up, however, the castor
angle is no longer correct and the tires may tend to track improperly. In fact, the
tires may actually tend to steer completely to one side or the other, at times quite
abruptly. This, of course, is an undesirable occurrence, which may give rise to maneuverability
difficulties or suspension damage.
[0005] Several technologies have been developed to address the aforesaid problem. The most
common is to use some form of a mechanical linkage which locks out the steerability
of the suspension (i.e. the wheels) when the vehicle is placed in its reverse operating
mode. Two currently known systems in use are the so-called "bar lock" and "pin lock"
systems.
[0006] In the "bar lock" system, a bar (or, more appropriately, a locking arm) is caused
to swing into locking position by air actuation employing appropriate valving off
of the brake chamber. When the locking arm swings into place, it engages an opening
in the tie bar plate of the suspension's steering mechanism. Since this plate is attached
to the tie rod of the steering mechanism and the arm is ultimately attached to the
axle, steering is prevented. The "pin lock" is somewhat similar to the bar lack system
in that it operates under the same principle, but uses an actuated pin instead of
a bar. When an air cylinder is actuated, it forces a spring loaded pin to move dawn
through an opening in the tie bar plate, thus rendering the steering mechanism inoperative.
[0007] The various lockout devices and techniques known prior to the subject invention have
one or more drawbacks associated with their use. For the most part, they are usually
difficult to install, are heavy and complex in the number of parts required to be
added to the suspension as additional items, and often require considerable maintenance.
Some have the potential for unreliable lockout engagement, and many require the use
of added shock absorbers or dampers because they, themselves, have no capability in
this regard.
[0008] In view of the above, it is apparent that there exists a need in the art far a lockout
mechanism which is not subject to the above drawbacks in the prior art. It is a purpose
of this invention to fulfill this need in the art, as well as other needs which will
become more apparent to the skilled artisan once given the following disclosure.
SUMMARY OF INVENTION
[0009] Generally speaking, this invention fulfills the above-described needs in the art
by providing a lockout mechanism for a self-steering suspension which far the first
time, and in a unique way, employs the internal cavity, and parts, of what in the
past has only been used as the aforesaid shock absorber-like damper for dampening
out oscillations and reducing wheel "shimmy". By making certain rather simple modifications
and additions to the piston rod and head of this known damper, a highly reliable,
yet easily installed and relatively lightweight lockout mechanism is achieved.
[0010] In certain embodiments of this invention, therefore, there is provided a lockout
mechanism for a self-steering, wheel-bearing axle suspension system of a vehicle,
the suspension system including a wheel-bearing axle, steering means for steering
the wheels of the system, and means for connecting the wheel-bearing axle and the
steering means in ride engaging relationship to a frame member of the vehicle; the
lockout mechanism comprising a cylinder connectable to the steering means, this cylinder
having a walled fluid reservoir within it, a substantially incompressible fluid (e.g.
liquid or gas) within the reservoir, a piston within the fluid reservoir having a
piston head slidable within the reservoir and extending across the fluid reservoir
in fluid-sealing engagement with the walls thereof so as to define a first fluid compartment
and a second fluid compartment separated from the first fluid compartment by the piston
head, the piston head having an orifice therein to thereby define a fluid flow path
between the first and second fluid compartments; the lockout mechanism further including
a valve associated with the piston head orifice for opening and closing the orifice
to flow of the fluid between the first and second fluid compartments, and a control
for actuating the valve to its open and closed positions; whereby when the orifice
is substantially fully closed the lockout mechanism prevents any substantial steering
of the wheels and when the orifice is open the wheels are steerable.
[0011] In certain further embodiments of this invention, the extent to which the valve of
the lockout mechanism is open determines the degree of ease of steerability of the
self-steering suspension. Controls are thus provided to accomplish a completely open,
partially opened, or completely closed fluid flow path. In this way, when the flow
path is completely closed the steering is effectively fully locked out because the
fluid in the reservoir is not allowed to flow between the two fluid compartments.
However, in certain other embodiments of this invention, sufficient fluid is allowed
to flow, as by incomplete tolerance between the piston head seal and the wall of the
reservoir, or by such inaccurate tolerance in the valve head, such that even in its
most locked out or fully closed mode the cylinder is effective to act as a shock absorber-type
damper to take up oscillations and prevent wheel "shimmy". In short, in such an arrangement
the lockout mechanism acts as a damper regardless of the mode of actuation or deactuation
in which it is placed. In still further embodiments, through the use of a pressure
regulator, the amount of closing off of the flow path by the piston is modulated such
that, for example, a high degree of lockout is effected if the vehicle makes a sudden
lane change, but significant steerability is provided if the vehicle is in a long
curve.
[0012] In still further embodiments the lockout mechanism is provided with one or two sensors.
One sensor operates to sense when the vehicle is in its reverse gear (direction of
travel) mode and activates lockout at that time. Another sensor operates to sense
a predetermined forward travel speed (e.g. 45 mph) such that at or above this speed,
lockout is actuated. Either one or both of these sensors may be employed.
[0013] This invention will now be described in relation to certain embodiments thereof as
set forth in the accompanying illustrations, wherein:
IN THE DRAWINGS
[0014] Figure 1 is a partial side plan view of a known type of wheel-bearing steerable lift
axle vehicle, but embodying a lockout mechanism according to the subject invention.
[0015] Figure 2 is a top plan view of the embodiment of Figure 1.
[0016] Figure 3 is a top plan view of a known type of steerable axle, but incorporating
therein an embodiment of a lockout mechanism according to this invention.
[0017] Figure 4 is a side sectional view of an embodiment of a lockout cylinder according
to this invention.
[0018] Figure 5 is a partial side sectional view of the valve mechanism illustrated in Figure
4 and further illustrating the flow path in its fully open position according to an
embodiment of this invention.
[0019] Figure 6 is a partial side sectional view of the valve mechanism of Figure 4, but
illustrating the flow path in its fully closed position.
[0020] Figure 7 is a schematic of an embodiment of a control mechanism according to this
invention.
[0021] Figures 8a and 8b are side plan views of the lift axle embodiment of Figure 1 in
its "raised" and road-engaging or "lowered" positions, respectively.
[0022] Figure 9 is a graph illustrating a typical modulating preset curve for the embodiment
of Figure 1 if modulation is to be incorporated in the system.
[0023] Figure 10 is a partial side sectional view of the valve of Figures 4-6 in its partially
open, modulated position as determined by preset established through the use of the
curves of Figure 9.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
[0024] Before describing in detail the illustrated embodiments, it is to be pointed out
that the term "lockout" as used herein is used in its conventional, but broad, sense.
That is to say, the term "lockout" is used herein to mean that steerability has been,
to some significant extent, made more difficult by effecting the lockout mode of the
mechanisms of this invention. Thus "lockout" may be either partial or full.
[0025] When, for example, the amount of lockout effected is referred to as "full" or "fully
closed" (with reference to the flow path), these terms are used to mean that no substantial
steerability may occur in the otherwise steerable wheels of the suspension system
involved. In some systems this may mean complete non-steerability and lockout against
any substantial oscillatory movement. In most systems contemplated, however, these
two terms are used to refer to a system wherein, while steerability by itself has
been effectively eliminated, the system still acts as an effective shock absorber
against oscillatory movements, including wheel "shimmy" during vehicle operation (e.g.
through leakage across the valve as aforesaid).
[0026] Reference is now made to Figures 1-2. In these Figures there is illustrated a lift
axle suspension which finds particular utility as an environment in which the lockout
mechanisms of this invention may be used. The suspension illustrated is an embodiment,
in this respect, of the unique steerable, wheel-bearing lift axle suspension systems
disclosed in our U.S. Patent No. 5,403,031. The entire disclosure of this patent is
incorporated herein by reference, including the discussion of the steerable nature
of the suspension by adjustment of the caster angle so as to render the suspension
self-steering. Also described therein is the nature of how the system is raised and
lowered in accordance with the unique bi-directional expansion and contraction features
of this patented system. Such features are prior art to the subject invention and
serve as an advantageous environment in which the lockout mechanism of this invention
may be efficiently and effectively employed.
[0027] By way of brief reference to this lift axle, illustrated in Figures 1-2, there is
illustrated a pair of parallel beams 1, 3 pivotally connected at their forward ends
by pivots 5a, 5b to hanger bracket 7 which, in turn, is bolted to longitudinal frame
member 9 of vehicle 11. Parallel beams 1 and 3 are pivotally connected at their rearward
ends to pivots 13a, 13b. Pivot 13a, of course, contains the mechanism as illustrated
(and as fully described in the aforesaid U.S. Patent No. 5,403,031) for adjusting
the castor angle α by turning eccentric cam 15 the requisite amount. (As illustrated
"kp" is the king pin center line and the adjustable angle is usually about +3° to
+6°.)
[0028] With reference next to Figures 8a, 8b a typical vehicle 11 is shown. Vehicle 11 has
a body 107, a wheel-bearing, non-liftable, non-steerable suspension 109 as a primary
means of support, and the wheel-bearing lift axle suspension of Figures 1, 2 generally
designated as 111. The roadbed, or ground, is generally designated as 113. Vehicle
11, in this respect, may be any type of vehicle which employs a steerable, liftable
or non-liftable axle suspension system. Examples include heavy duty dump trucks, semi-trailers,
and the like.
[0029] Figures 1 and 8b illustrate suspension 111 in its "lowered" or "road-engaging" position.
Figure 8b, of course, shows suspension 111 in its "lifted" or "raised" position. As
described and illustrated more fully in the aforesaid U.S. Patent No. 5,403,031, raising
and lowering of suspension 111 is accomplished by the expansion and contraction of
air bellows 17 and 19, respectively. Bellows 17, in this respect, is connected at
its upper end to frame 9 and at its lower end to pedestal 21 on axle seat member 23
which, in turn, is connected to axle 25. Axle 25, in turn, is connected to wheel (and
tire) 27. It is understood, of course, that Figures 1-2 illustrate only one side of
a typical vehicle and that the suspension in complete form is actually duplicated
on the other side of the vehicle with axle 25 being a linking structure therebetween.
Thus, by expanding bellows 17 and exhausting bi-directional bellows 19, wheels 27
are lowered into road engagement with ground surface 113. By expanding bi-directional
bellows 17 (connected between brackets 29a, 29b attached to beams 1, 3 respectively,
for bi-directional expansion) and exhausting bellows 17, wheels 27 are lifted from
road engagement as shown in Figure 8a. Air controls, using the brakes' air source,
for accomplishing the lifting and lowering, are conventional and well known in the
industry.
[0030] As aforesaid, suspension 111 is rendered steerable when in road engagement as illustrated
in Figures 1-2 and 8b by appropriate adjustment of the caster axle, e.g. to a positive
caster angle α of about 3° - 6°. Steerability is conventionally provided by a typical
steering mechanism which includes a steering arm 31, and tie rod 33, which together
with a conventional spindle arrangement (not shown) steerably connects the wheel to
the axle. When such steerability is effected, there arises a need at times to provide
a lockout mechanism for controlling steerability. As stated above, it was known prior
to this invention to provide in this steering mechanism a simple stabilizer which,
from all outward appearances, looked the same as lockout cylinder 35. Optionally,
furthermore, such stabilizers were provided with a self-centering coil spring 37 of
known construction. Prior to this invention, however, such stabilizers were merely
used to dampen oscillations including wheel "shimmy" during vehicle operation. They
had no substantial or significant retarding effect upon steerability. Thus if one,
prior to our invention, desired a lockout feature in a steerable suspension, significant
additional expense, time, weight, and installation costs had to be incurred to add
a lockout mechanism which was separate from this stabilizer (e.g. the aforesaid "bar"
or "pin" lockout mechanism).
[0031] It is, therefore, a unique feature and distinct advantage of this invention that
full lockout may be provided on selective demand without the need for such an additional
lockout mechanism. Rather, this invention achieves a portion of its uniqueness by
using, through modification, the otherwise conventional inner structure of the conventional
shock absorber-like stabilizers of the past to achieve the desired lockout features.
In certain embodiments, in fact, it is contemplated that lockout is achieved while,
at the same time, maintaining the dampening features of the known stabilizers even
when the system has locked out steerability. In such embodiments the need to add an
additional, separate lockout mechanism or stabilizer to the suspension is eliminated.
[0032] Figure 2 (Fig. 1 being a side view thereof), in this respect, illustrates lockout
cylinder 35 in a position either in straight ahead mode or as wheel 27 steers at an
angle Θ to go through a turn (partial wheel shown). As can be seen, the typical shock
absorber-like structure of lockout cylinder 35 has expanded (during the turn) so as
to separate dustcover 39 from reservoir housing 41, exposing piston rod 43. It is
to be remembered, in this respect, that in the most usual embodiments, the system
illustrated in Figures 1-2 is duplicated on the other side of the vehicle such that
lockout cylinder 35 on that other side is facing in the opposite direction, thus to
provide a mechanism which functionally handles both wheels equally as each turns according
to the connecting linkage achieved by tie rod 33 and respective steering arms 31 on
either side of the vehicle.
[0033] The nature of this steering linkage, as well as a manner of attachment of lockout
cylinders 35 to the various other parts of the system, is best illustrated in Figure
3. In this Figure, the tires have been removed from wheels 27 for better viewing of
the system. Spring brakes 45 are, however, illustrated . As depicted, the end of piston
rod 43 having cover 39 of lockout cylinder 35 is connected via brackets 47 to axle
25, while the opposite end of cylinder 35, namely, the reservoir end, is pivotally
connected to steering arms 31 by pivot connections 49. In this way, lockout cylinders
35 are connected in opposite direction, one from the other, thereby to oppose each
other functionally so as to appropriately handle oscillations and wheel shimmy, as
well as steering in the two opposing wheels 27. Axle pads 51 are, of course, the locus
for axle seat member 23 and air bellows 17. It is also to be stated that lockout cylinders
35 may be optionally provided with self-centering coil springs 37 if desired, as illustrated
in Figure 2.
[0034] As alluded to above, a skilled artisan viewing the embodiments of Figures 1-3 externally,
would not normally be able to tell the difference between the prior art embodiments
using non-lockout, shock absorber-like stabilizers and the subject invention, except
for air lines 53 (see Fig. 3) that are connected to the end of each piston rod 43
(described more fully below). However, if that same skilled artisan were to disassemble
what might normally be considered only a shock absorbing damper or stabilizer, the
difference would become immediately apparent. This difference is best illustrated
with reference to Figures 4-6 and 10.
[0035] With reference first to Figure 4, lockout cylinder 35 includes pivot connection 49,
reservoir housing 41, dustcover 39 and piston rod 43. In conventional fashion dustcover
39 is connected to piston rod 43, so as to move therewith. Piston rod 43 is connected
at one end to piston head 55. Piston head 55 extends across the internal cavity of
reservoir housing 41 and sealingly, but slidingly, engages inner wall 57 of housing
41, which inner wall 57, together with end caps 59, 61, defines a fluid reservoir
63 therein. As thus constructed, piston head 55 separates reservoir 63 into a first
fluid compartment 65 and a second fluid compartment 67. Since end 69 of piston rod
43 is connected to, for example, axle 25, while connection 49 is connected to steering
arm 31 (or vice versa), the structure as shown provides a typical shock absorbing,
stabilizer function due to the formation of a fluid flow path in piston head 55 such
that first compartment 65 is in fluid flow communication with second compartment 67.
[0036] In this respect, reservoir 63 is generally substantially filled with a hydraulic
(i.e. an incompressible) fluid. However, other "fluids", i.e. defined herein broadly
as liquids or gases, or combinations thereof, can be used if so desired. Thus by restricting
the size of the flow path through an orifice(s) 71 in the piston head between compartments
65, 67 a damper is provided to control oscillation and wheel shimmy as piston head
55 slides within wall 57 due to oscillations that force fluid from one compartment
to the other.
[0037] Now, for the first time, this invention modifies this internal, and otherwise conventional,
structure so as to achieve a unique lockout mechanism. This is accomplished by the
formation of at least one, and usually two or more, lateral orifice(s) 75 at the piston
head end of piston rod 43 and an intersecting longitudinal orifice 77 extending centrally
through the length of piston rod 43 which ultimately communicates with piston head
orifice 71. In this way, a fluid flow path is formed between first fluid compartment
65 and second fluid compartment 67. Then, by the inclusion of an adjustable valve
mechanism 79 at the interface of orifices 71, 75 and 77, a unique lockout mechanism
is provided.
[0038] An embodiment of a valve mechanism 79 as contemplated herein and as illustrated in
Figure 4, is also illustrated in Figures 5-6. While the mechanism shown in these Figures
is in the nature of a sliding spool valve, it is understood that various other types
of valves may be used, such as a ball valve, to accomplish the same results. Such
other types of valves are thus considered to be a "valve" within the meaning of this
term as used herein and thus within the scope of our invention.
[0039] As illustrated, valve 79 is located at the intersection of piston head orifice 71,
lateral piston rod orifice 75 and longitudinal piston rod orifice 77. Valve 79 includes
a spool 81 provided with a pair of end lands 83 separated at their circumferential
edges by a sealing O-ring 85. A further sealing O-ring 87 is provided at the other
end of spool 81 similarly separating two land portions 89. Valve 79 further includes
a spring retaining cap 91 which has a central orifice 93 aligned with piston head
orifice 71. Spring retaining cap 91 is cup-shaped, so as to house in its internal
cavity biasing coil spring 73.
[0040] Biasing coil spring 73 has a diameter and spring coil size which, together with the
spacing between each contiguous coil, does not adversely affect the flow of fluid
through orifices 75, 77, 93 an 71 (or vice versa). Such orifices, in this respect,
define and form a fluid flow path FFP communicating first fluid compartment 65 with
second fluid compartment 67 (Fig. 4). Coil spring 73 extends in compression between
the internal end wall 97 of cap 91 and the end wall 99 of land 83 in this flow path
as illustrated.
[0041] As shown in Figure 5, coil spring 73 normally biases sliding spool 81 to a position
where rear wall 99 clears orifice(s) 75 and thereby presents no obstruction to fluid
as it flows through flow path FFP. This position may be referred to as the "fully
open" position. In such a position valve 81 is inoperative for any lockout function
and lockout cylinder 35 serves as a typical and effective damper (stabilizer) against
articulation forces which cause oscillations and wheel shimmy without, at the same
time, having any substantial effect upon the designed in steerability of the suspension.
[0042] As can be seen, O-rings 85 and 87 act to seal longitudinal orifice 77 from fluid
communication across spool 81. This, in turn, enables the end of orifice 77 adjacent
land 89 (as opposed to that portion of orifice 77 at the other end of spool 81 contiguous
wall 99) to be used for air (or other fluid) actuation of spool 81 to a fully closed
or partially open position. In Figure 5 the arrow A indicates by direction the evacuation
of air from orifice 77, thus allowing the normal bias of coil spring 73 to hold spool
81 against its rear stop wall 101 so as to be in its "fully open" position.
[0043] As shown in Figure 6, when air or other fluid is applied at a sufficient pressure
in orifice 77 at, and in the direction of, arrow A, spool 81 (including lands 83)
is caused to move across the intersection of lateral orifice 75 and longitudinal orifice
77 impeding the flow of fluid through flow path FFP as it progresses. Obviously, in
order for this to occur, sufficient force must be applied by the air in the direction
of arrow A to overcome the bias of coil spring 73. Finally, if sufficient air pressure
is applied, spool 81 will slide to the point illustrated in Figure 6 where preferably
both lands 83 (or only land 83 with wall 99 if so desired) clears orifice(s) 75. This
position is aptly designated the "fully closed" position since, except for designed
in or undesigned leakage across O-ring 85, no fluid can flow between first fluid compartment
65 and second fluid compartment 67. When this "fully closed" position is achieved,
steerability of the suspension is fully locked out and dampening can take place only
by way of the aforesaid designed or undesigned leakage in the valve itself (e.g. as
by passage around O-rings 85). A further embodiment of this invention, wherein the
air pressure is only sufficient to partially close orifice 75 will be described with
respect to Figures 9-10 below.
[0044] By the above structure a valve is provided which defines three basic positions: (1)
fully open, (2) partially open, and (3) fully closed. In the "fully open" position
(Fig. 5), the suspension is free to steer to the full degree of its design as determined
by the adjusted caster angle α. Only oscillations are dampened due to the nature of
the flow path FFP which is significantly less than the diameter of fluid reservoir
63. In the "partially open" (i.e. "partially closed") position, sufficient interruption
of fluid flow in flow path FFP is effected so as to reduce, i.e. lock out to some
extent, the steerability of the suspension generally, in proportion to the amount
of closing of flow path FFP effected (see Fig. 10 below). In the "fully closed" position
(Fig. 6) steering, for all intents and purposes, is fully locked out. Then, by allowing,
as aforesaid and optionally, for some designed in leakage, such as across lands 83
and O-ring 85 when valve 79 is "fully closed", a measure of dampening can be effected
even though steering, for all intents and purposes, is fully locked out. Still further,
or as yet another alternative, only one of the two cylinders 35 in the suspension
(see Fig. 3) need be provided with this invention. The other may be a prior art damper.
Still further, but less desirable, prior art dampers or shock absorbers may be provided
in addition to the two valved lockout cylinders 35 of this invention. In whatever
configuration chosen, by simple evacuation (e.g. release of the air pressure) in orifice
77 (in the direction of arrow A in Fig. 5), coil spring 73 automatically returns spool
81 to the fully open position shown in Figure 5.
[0045] Various controls from simple to complex, depending upon the number of functions to
be performed, may be designed to actuate valve 79. An exemplar embodiment is schematically
illustrated in Figure 7. Here, a control is provided with various options for sensing
when the vehicle is placed either in a reverse (or any other pre-selected) gear mode
and in response thereto locking out (fully or partially) the steering capability of
the suspension and/or sensing when the vehicle has reached a speed at or above which
lockout is desirable (e.g. 45 mph). In addition, and as illustrated, this same control
has the capability of raising and lowering the lift axle. While this embodiment shows
a combination of all three functions, it is understood that any selected control need
have only one function. For example, in a non-liftable, steerable axle suspension,
the lifting mode is not present and the control may employ either one or both of the
sensors. An additional modulating option is also provided in Figure 7, and will be
discussed with respect to Figures 9-10 below.
[0046] With reference now to the particulars of Figure 7, there is illustrated a conventional
air reservoir 201 having an inlet 203 from a source of compressed air (e.g. the vehicle's
air brake compressor, not shown for convenience). Exit line 205 from reservoir 201
leads to a conventional air brake protection valve schematically illustrated at 207.
Typically, and in accordance with law in certain jurisdictions, brake protection valve
207 is provided so as not to allow air to be drawn off the brake system unless a minimum
of 75 psi is achieved in reservoir 201.
[0047] A conventional air control kit is schematically illustrated at 209. This kit 209
includes pressure regulator 211, a manual two position valve 213, and pressure gauge
215. Kit 209 is used to regulate air to the air bellows in order to raise and lower
the lift axle as aforementioned. For example, when valve 213 is in one position air
is supplied to air ride bellows (springs) 17 and lift axle air bellows 19 are exhausted,
thereby placing the suspension in its "lower" or "road engaging" position. In the
other position, bellows 17 are exhausted and bellows 19 bi-directionally expand to
lift wheels 27 out of road engagement to their "raised" position (as per our aforementioned
patent). For convenience, a quick release valve 217 is provided for decreasing the
time required to exhaust air from bellows 17 when wheels 27 are lifted.
[0048] The control governing the lockout features of this invention is generally illustrated
at 219. As schematically illustrated, such a control conveniently includes an electronic
solenoid valve 221 positioned as illustrated to be normally closed and to have a ground
lead 223. At least one, and optionally two, sensor leads 225, 227 are further provided.
Lead 225 may be connected to a conventional sensor for sensing the speed of the vehicle
(e.g. from the electronics in the transmission), while lead 227 may be connected to
sense when the vehicle is placed in its reverse gear mode, such as by a sensor connected
to the reverse lights. In this manner, reverse travel and/or preselected highway speeds
may be sensed, automatically, for lockout of the steerable wheels 27.
[0049] For example, in normal forward operation of a typical heavy duty truck or semi-trailer,
air pressure (usually above 75 psi) is provided via line 229 from reservoir 201 through
brake protection valve 207 to both air kit 209 and lockout control solenoid 221. Air
kit 209 can then be used to both manipulate the lift axle and provide a constant air
pressure to bellows 17 when the suspension is in its road engaging mode. Air provided
via line 231 from line 229 to solenoid 221 is stopped because solenoid valve 221 is
biased to be normally closed. When, then, a signal is received from either lead 225
or 227, the spool in valve 221 is shifted to open the output port of the valve and
activate lockout. In this manner an effective lockout mechanism is achieved for both
(or either) reverse travel and/or forward travel above a prescribed speed (e.g. 45
mph).
[0050] Figure 7 further illustrates an additional and rather unique feature optionally incorporatable
into the subject invention. First of all, it is clear from the above description that
by modulating the air pressure applied to spool 81 in valve 79, the amount of steerability,
or, in other words, the amount of retardation of the designed in steerability in the
flow path FFP is regulatable simply by controlling the amount of closing of the flow
path FFP. To effect such modulation, if desired, pressure regulator 233 may be provided.
While such a regulator 233 may be very sophisticated, and even computer controlled,
to yield varying degrees of pressure in response to varying load inputs, etc., on
the lockout cylinders 35, regulator 233 may also effectively be a simple preset regulator
(as illustrated), i.e. a regulator set to provide a simple, pre-selected single pressure
to orifice 77 in piston rod 43.
[0051] The choice of a preset pressure is well within the capabilities of a skilled artisan.
Generally, it merely requires the balancing of the air pressure needed to achieve
the desired degree of closure of flow path FFP by spool 81 against the biasing (opening
force) of coil spring 73. Figure 10 illustrates the positioning of end wall 99 when
this balance is achieved, thus achieving a "partially open" position. As can be seen,
by providing a preset pressure from regulator 233 (via arrow A) to the rearward end
of spool 81, the bias of coil spring 73 is sufficiently overcome so as to move land
99 across orifice 75 a pre-selected distance, thereby to significantly retard, but
not to fully lock out, steering.
[0052] There are numerous instances where such an optional modulating feature may be desirable.
For example, it is clear to the skilled artisan that in most instances it may be very
important to fully lock out during reverse mode travel, but during forward travel
some steerability should be left in the system (by modulation to a "partially open"
position) so as to allow steering in long, slow curves even when the speed of the
vehicle is above the selected maximum speed for locking out the steering. In such
an instance, sensing in the reverse mode would by-pass regulator 233 (by-pass not
shown for convenience), but sensing in the forward mode would send the air line pressure
(e.g. 120 psi) in line 231 through the regulator which would lower the pressure to
the desired amount (e.g. 50 psi) so as to present spool 81 in the partially open position
shown in Figure 10.
[0053] One technique for choosing the appropriate pressure for regulation may be described
with reference to Figure 9. Such a technique includes instrumenting an exemplar vehicle
with the particular model and size steerable axle desired, such that steer axle steering
vs. time can be accurately monitored. Instrumentation adaptable for such use is well
known to the skilled artisan and, of course, includes an adjustable regulator. The
vehicle is then subjected to a series of high speed lane change maneuvers and long,
sweeping curves in the highway. The regulator air pressure is then varied until the
steering angle change during high speed lane change maneuvers is negligible, while,
at the same pressure, the axle (wheels) tracks around the long, sweeping curves. The
cylinders 35 on the axle are then removed and one of them is placed into a conventional
press that monitors load vs. deflection. With the pressure regulator set at the same
pressure that was used to optimize the performance characteristics on the highway,
the cylinder is then subjected to a load and the deflection is monitored. As a guideline
to the skilled artisan in how to carry out this invention, an exemplar load vs. deflection
(creep) curve is set forth in Figure 9 for a typical cylinder 35 found useful in lift
axles for heavy duty trucks of the steerable lift axle type disclosed and illustrated
in our aforesaid U.S. Patent No. 5,403,031. In Figure 9 the dotted line is load and
the solid line is creep. From this exemplar, then, a preset pressure is determined
which can then result, if desired, in the use of a simple preset, non-adjustable regulator
for all similar types of vehicles and suspensions. From the curves the characteristics
of cylinders 35 for similar further suspensions are thereby established, and clone
cylinders selected accordingly.
[0054] In order to give the skilled artisan a further guideline for practicing this invention,
rather than by way of limitation, a useful lockout cylinder 35 for use in a typical
lift axle suspension, such as those disclosed and illustrated in our aforesaid U.S.
Patent No. 5,403,031, starts with a standard shock absorber such as made by Gabriel
Corporation, Part No. 1TX695334, a well known 1 5/8" bore shock absorber. Such a shock
has a cylinder with an O.D. for the dust collector of 3.25" and an O.D. for the reservoir
of 2.75 inches. The reservoir holds 1018cc of hydraulic fluid. The shock has an extended
length of 23.66 inches, a collapsed length of 17.16 inches, and thus a stroke of 6.50
inches. This shock is then modified by providing a longitudinal orifice 77 of 0.30
inches in diameter, and 2 lateral orifices 75 of 0.30 inches in diameter. Outlet orifice
71 and cap orifice 93 are substantially the same and are 0.188 inches in diameter.
The following comprises its performance characteristics when fully open:
|
Velocity (in/sec) |
Damping Force (LBF) |
4.71 |
13.35 |
26.70 |
Rebound |
720 |
950 ± 190 |
1212 |
Compression |
113 |
198 ± 50 |
254 |
[0055] Such a cylinder 35, now modified, is useful in the embodiment where reverse lockout
and/or highway speed lockout is desired. Two such cylinders 35 may then be employed
as cylinders 35 as shown in Figure 3 and operated effectively by using the controls
of Fig. 7 as described above.
[0056] Once given the above disclosure many other features, modifications and improvements
will become apparent to the skilled artisan. Such other features, modifications and
improvements are therefore considered to be a part of this invention, the scope of
which is to be determined by the following claims:
1. A lockout mechanism for a self-steering, wheel-bearing axle suspension system of a
vehicle, said suspension system including a wheel-bearing axle, steering means for
steering said wheels of said system and means for connecting said wheel-bearing axle
and said steering means in ride engaging relationship to a frame member of said vehicle;
said lockout mechanism comprising a cylinder connectable to said steering means, said
cylinder having a walled fluid reservoir therein, a substantially fluid within said
reservoir, a piston within said fluid reservoir having a piston head slidable within
said reservoir and extending across said fluid reservoir in fluid-sealing engagement
with the walls thereof so as to define a first fluid compartment and a second fluid
compartment separated from said first fluid compartment by said piston head, said
piston head having an orifice therein thereby to define a fluid flow path between
said first and second fluid compartments;
said lockout mechanism further including a valve associated with said piston head
orifice for opening and closing said orifice to flow of said fluid between said first
and second fluid compartments, and a control for actuating said valve to its open
or closed position;
whereby when said orifice is substantially fully closed said lockout mechanism prevents
any substantial steering of said wheels and when said orifice is open said wheels
are steerable.
2. A lockout mechanism according to claim 1 wherein the ease of steerability of the wheels
is in proportion to the extent to which said orifice is open.
3. A lockout mechanism according to claim 1 wherein said mechanism acts as a dampening
device against wheel oscillation when said orifice is open, partially open, and closed.
4. A lockout mechanism according to claim 1 wherein said mechanism further includes a
spring located in said first fluid compartment which normally biases said piston head
toward said second fluid compartment.
5. A lockout mechanism according to claim 4 wherein said piston further includes a piston
rod connected to said piston head extending outwardly through said second fluid compartment
beyond one end of said cylinder, said piston rod having a longitudinal orifice therein
connected to said control and a lateral orifice therein intersecting said longitudinal
orifice, said lateral orifice being a part of said fluid flow path between said second
fluid compartment, said piston head orifice, and said first fluid compartment,
said valve for opening and closing said piston head orifice including a valve head
movably located in said longitudinal orifice with respect to said lateral orifice
so as to selectively interrupt or not interrupt fluid flow between said longitudinal
and lateral orifice and so as to be movable into a position in said intersection between
said longitudinal and lateral orifice thereby to close off said fluid flow path between
said first and second fluid compartments and thereby prevent any substantial steering
of said wheels.
6. A lockout mechanism according to claim 5 wherein said valve further includes a spring
normally biasing said valve head to a position within said longitudinal orifice so
as to not interrupt said fluid flow between said longitudinal and lateral orifice
and thereby normally open said fluid flow path between said first and second compartments.
7. A lockout mechanism according to claim 6 wherein said control includes an actuator
for selectively providing air to said longitudinal orifice under a pressure sufficient
to overcome the bias of said spring normally biasing said valve head and to move said
valve head to a position which closes said fluid flow path, and for selectively eliminating
said air under pressure thereby to allow said normal bias of said spring to return
said valve head to a position which re-opens said fluid flow path.
8. A lockout mechanism according to claim 7 wherein said actuator is capable of controlling
said air pressure thereby to selectively move said valve head to a position which
closes off said fluid flow path either partially or fully.
9. A lockout mechanism according to claim 1 wherein said lockout mechanism includes two
said cylinders and a connection for connecting each said cylinder to an opposite side
of said suspension.
10. A lockout mechanism according to claim 9 wherein said steering means of said vehicle
includes a first and a second steering rod, each steering rod being located at a respective
side of said vehicle and a tie rod extending between said first and second steering
rods and connected in steering engagement with said rods, and wherein said lockout
mechanism includes means for connecting a said cylinder to a respective said steering
rod such that each said cylinder can be attached so as to be in an operatively opposing
direction with respect to the other said cylinder.
11. A lockout mechanism according to claim 10 wherein said lockout mechanism further includes
means for connecting each said cylinder to said axle.
12. A lockout mechanism according to claim 1 wherein said lockout mechanism includes a
sensor for sensing when said vehicle is in a reverse gear mode and an actuator for
actuating said valve to a closed position in response to said sensor sensing that
the vehicle is in said reverse gear mode.
13. A lockout mechanism according to claim 1 wherein said lockout mechanism includes a
sensor for sensing when said vehicle reaches a predetermined speed and an actuator
for actuating said valve to a closed position when said vehicle is operated at or
above said predetermined speed and for actuating said valve to an open position when
said vehicle is operated below said predetermined speed.
14. A lockout mechanism according to claim 13 wherein said lockout mechanism further includes
a sensor for sensing when said vehicle is in a reverse gear mode and an actuator for
actuating said valve to a closed position in response to said sensor sensing the vehicle
being placed in said reverse gear mode.
15. A lockout mechanism according to claim 14 wherein said vehicle includes reverse gear
backup light electric circuitry and said sensor for sensing said reverse gear mode
includes a connection for connecting said sensor to said backup light electric circuitry.
16. A lockout mechanism according to claim 15 wherein said vehicle includes an electronic
transmission circuitry capable of indicating the speed of travel of said vehicle and
said sensor for sensing said predetermined speed of said vehicle includes a connection
for connecting said sensor to said electronic transmission circuitry.
17. A lockout mechanism according to claim 1 wherein said control is capable of actuating
said valve to a closed position when said wheels are in a turned position.
18. A lockout mechanism according to claim 1 wherein said mechanism further includes a
sensor for sensing load inputs to said vehicle above a predetermined speed, and in
accordance with the amount of said load input incurred, actuating said control so
as to vary the amount of closing of said valve in proportion to the said load input
sensed.
19. A lockout mechanism for a self-steering, wheel-bearing axle suspension system of a
vehicle comprised of a wheel-bearing axle, steering means, and shock absorber means
for stabilizing oscillations in said system when in motion, said lockout mechanism
including means located within said shock absorber for locking out said steering means.
20. A lockout mechanism according to claim 19 wherein said shock absorber includes a cylinder
portion having therein a fluid reservoir and a piston head so located in said cylinder
so as to define on either side of said piston head a fluid compartment, said piston
head having an orifice therein to define a normally shock absorbing fluid flow path
between said fluid compartments, said means located within said shock absorber for
locking out said steering means includes means for selectively opening and closing
said shock absorbing fluid flow path between said fluid compartments.
21. A lockout mechanism according to claim 20 wherein said lockout mechanism further includes
sensor means for sensing when said vehicle is in a reverse driving mode and actuator
means responsive to said sensor means for actuating said lockout mechanism to a position
closing said fluid flow path when said sensor means senses said vehicle in a reverse
driving mode.
22. In a frame-membered wheeled vehicle having a wheel-bearing axle suspension system
connected to the frame member of said vehicle, said system including a wheel-bearing
axle, self-steering means for steering said wheels of said system, means for connecting
said system to a said frame member of said vehicle and a lockout mechanism for preventing
said steering means from steering said wheels at selected times, the improvement comprising
wherein said lockout mechanism includes a cylinder connected to said steering means,
said cylinder having a walled fluid reservoir therein, a fluid in said reservoir,
a piston within said fluid reservoir having a piston head slidable within said reservoir
and extending across said fluid reservoir in fluid-sealing engagement with the walls
thereof so as to define on either side of said piston head a respective first fluid
compartment and a second fluid compartment, said piston head having an orifice so
as to establish a fluid flow path between said first and second fluid compartments;
said lockout mechanism further including a valve means associated with said orifice
for opening and closing said orifice to flow of said fluid between said first and
second fluid compartments, and a control means for actuating said valve means to its
open and closed positions;
whereby when said orifice is fully closed said lockout mechanism prevents any substantial
steering of said wheels and when said orifice is open said wheels are steerable.
23. In the frame-membered wheeled vehicle according to claim 22 wherein said lockout mechanism
is effective as a shock absorber against wheel oscillation in whatever mode of actuation
or deactuation the lockout mechanism is placed.
24. In the frame-membered wheeled vehicle according to claim 22 wherein said vehicle includes
a transmission having a reverse gear mode, and wherein said lockout mechanism includes
sensor means for sensing when said transmission is in a reverse gear mode, and wherein
said control means includes means for actuating said valve means to a closed position
in response to said sensor means sensing said vehicle in a said reverse gear mode.
25. In the frame-membered wheeled vehicle according to claim 22 wherein said vehicle includes
a means for indicating the speed of said vehicle in the forward direction and wherein
said lockout mechanism includes sensor means connected to said speed indicator means
for actuating said valve means to a closed position in response to said sensor means
sensing a speed above a predetermined amount.
26. In the frame-membered wheeled vehicle according to claim 25 wherein said vehicle includes
a transmission having a reverse gear mode and wherein said lockout mechanism includes
sensor means for sensing when said transmission is in a reverse gear mode, and wherein
said control means includes means for actuating said valve means to a closed position
in response to said sensor means sensing said vehicle in a said reverse gear mode.
27. In the frame-membered wheeled vehicle according to claim 24 or 25 wherein said lockout
mechanism is effective as a shock absorber against wheel oscillation in whatever mode
of actuation or deactuation the lockout mechanism is placed.